Infections caused by herpes simplex virus type 1 (HSV-1) and the related viral serotype HSV-2 are among the most common human infections. One of the important features of the virus is its envelope or membrane. Among the viral proteins found in this envelope are the viral glycoproteins, gB, gC, gD, dE, gG, and gH. These glycoproteins are the first virion components to come in contact with the host cell and are involved in virion attachment and penetration. Later in virus replication they become involved in envelopment and egress. Important questions concerning the role of the glycoproteins in these processes remain unresolved. There are also a number of fundamental questions concerning basic glycoprotein properties, such as membrane anchoring, which need to be answered. HSV-1 gC is a nonessential viral glycoprotein which can be used as a model glycoprotein to answer certain questions concerning membrane anchoring. The role of the transmembrane domain has been well established. Preliminary data indicate that the cytoplasmic domain is also important, perhaps due to charged amino acid residues that cannot pass through the membrane. Oligo nucleotide directed mutagenesis will be used to create additional gC mutants affected in this domain. Also, the process by which gC becomes incorporated into the virion envelope will be studied by use of an antibody selection technique to select and identify mutants which produce gC but fail to incorporate it into the virion. HSV-1 gB has been implicated in the membrane fusion process, both in penetration and cell fusion. Structural and genetic studies have identified the cytoplasmic and transmembrane domains of gB as important in the fusion process. Oligonucleotide mutagenesis will be used to construct gB mutants designed to explore the structure of this glycoprotein and to examine its role in membrane fusion. A gene apparently encoding a nonglycosylated membrane protein has also been identified, although the protein itself has not been found, perhaps because it is extremely hydrophobic. Several methods will be used to identify the primary translation product of this gene, including the production of antibodies against synthetic peptides and in vitro translation of messenger RNA.